DE 10 2009 024 026 A1 describes a control valve for a camshaft adjuster, including a hollow control piston which is movably guided within a valve housing. Arranged within the piston cavity is a hydraulically unlockable check valve which opens a first pressure medium line in the inflow direction, the check valve having a closing part which has a sealing surface and by way of which the at least one valve opening is closable. The closing part is designed in the form of a spiral-wound band and is elastically deformable, as a result of which the sealing surface thereof is movable into a closed position, in which the sealing surface rests sealingly against the valve opening, and into an open position, in which the valve opening is fully open. Also located on the closing part is an integrally formed support section for the axial support of the closing part on the control piston.